Recent developments in Internet technology contribute to the popularization of digital information technology of precision electronic devices such as computers, and user friendliness is being improved.
On electronic devices such as personal computers there are mounted various devices using mechanical mechanisms, which include a storage device such as a hard disk drive (HDD) or a magneto-optical memory, a cooling fan, and a piezoelectric backlight power supply. For example, a storage device for a personal computer includes a magnetic recording medium, a magnetic head, a slider, a head arm, a voice coil motor, and the like.
Such storage devices have high densities and large capacities. Since the storage device handles valuable information data such as image or video data, or analysis data, high reliability is required. However, such storage devices include many mechanism elements and mechanical parts, and are prone to failure due to disturbances such as impact and vibration.
Moreover, while used for a long time, these mechanism elements and mechanical parts of the storage device may generate abnormal vibration associated with deterioration or the like due to the long-term use.
Therefore, a sensor for detecting disturbances received by the storage device, or vibration generated by the storage device itself, more specifically, a vibration sensor for detecting acceleration, speed, and displacement is mounted on the storage device.
Detection performance of the vibration sensor differs depending on in which direction is the storage device vibration to be detected. Moreover, detection accuracy differs depending on the attachment position or the attachment method of the vibration sensor, in addition to the performance of the vibration sensor itself.
An abnormality in the storage device is reflected in the behavior of the recording medium or the head arm. Therefore, it is desired that the attachment position of the vibration sensor is mainly in an in-plane direction of the recording medium and in a direction perpendicular to the surface thereof. Thus, by detecting vibrations in two directions of the recording medium, detection performance for abnormalities in the storage device is improved.
As a conventional method for detecting vibrations in two different directions, an acceleration detection device capable of independently detecting acceleration in two directions orthogonal to each other by using two acceleration sensors has been proposed (refer to Patent Document 1).
FIG. 10 is a perspective view showing the acceleration detection device. This acceleration detection device 101 includes an acceleration sensor 103 and an acceleration sensor 104. The acceleration sensor 103 and the acceleration sensor 104 are attached on a sensor attachment plane 102, inverted by 180 degrees to each other in the sensor attachment plane 102.
A maximum-sensitivity axial direction PA of the acceleration sensor 103 with respect to the sensor attachment plane 102 and a maximum-sensitivity axial direction PB of the acceleration sensor 104 with respect to the sensor attachment plane 102 are inclined with respect to the sensor attachment plane 102 by an angle θ.
The acceleration detection device 101 is provided with an arithmetic section that calculates a sum (SA+SB) of an output SA and an output SB of the two acceleration sensors 103 and 104, and an arithmetic section that calculates a difference (SA−SB) between the respective outputs SA and SB. The acceleration detection device 101 detects acceleration in a direction perpendicular to the sensor attachment plane 102 from the sum (SA+SB), and acceleration in a direction parallel to the sensor attachment plane 102 from the difference (SA−SB), respectively independently.
As a result, acceleration in two directions orthogonal to each other can be detected independently. Moreover, because the identical two acceleration sensors are used, manufacturing cost of the acceleration sensor can be reduced, and further, thinning of the product can be realized.
Conventionally, an attachment position of the vibration sensor has been any position of a control circuit board of a storage device, inside the storage device, and an exterior part of the storage device. Because the acceleration sensor described above is a surface-mounted chip part, it is attached to the control circuit board of a storage device or inside the storage device by a solder joint.
Moreover, a storage device that reduces noise by suppressing vibration by a vibration sensor has been proposed (refer to page 7 in Patent Document 2).
This storage device has a configuration in which a vibration sensor is fixed to a surface of a top cover of the storage device by an adhesive. The storage device suppresses vibration transmitted from a head assembly to the top cover to realize low noise, by feeding back an output of the vibration sensor to an actuator attached to the top cover.